U.S. Pat. No. 5,602,348 (Takakarhu and Nyfors) purports to disclose a method and an equipment for taking a sample from a slurry. The slurry flow was set at a sufficiently high rate in order to avoid immobilization of particulates on the filter face. A pressure gradient was used to extract the sample from the slurry. Regeneration of the filter membrane to its original state was not addressed.
U.S. Pat. No. 4,501,161 (Endo et al.) purports to disclose an autosampler for sampling from a suspension. According to their claim, two filtering tubes, which are connected to a sampling cell, are immersed in a test solution during sampling. A circulatory pump is used to circulate fluid through the filter membranes and a portion of the test solution enters into the filtering tubes. The filtered solution is sampled from the sampling cell and the residual test solution is returned to the suspension. The residual test solution cannot be analysed. The filtering tubes are immersed in a fluid container and are not suitable for sampling from a flow operation. The sampling mechanism leads to a build-up of residue in the slurried suspension overtime and is not suited for continuous operation.
US Pat. Appl. US 2010/0224012 A1 (Modic et al.) purports to disclose a fluid sample delivery system for filtering solid particles from a liquid sample. The filter membrane comprises three layers of membrane of varying porosity. A displacement plunger with a needle is used to draw samples from a vial or a set of vials on a carousel. A controller, which is capable of monitoring the needle drive slippage, is programmed to detect obstruction and adjust filtering speed to minimize obstructions in the filter membrane. The disclosure does not have a mechanism to restore the filter membrane in its original state for sustainable continuous operation.
U.S. Pat. No. 5,389,244 (Cranston) purports to disclose an enclosed filtration device for hazardous sampling. A circulatory pump was used to receive heterogeneous fluid onto a filter membrane and a set of valves was used to open and close the filtrate line in order to complete the filtration process. The unit required the replacement or the cleaning of the filter membrane between runs. The bottom dish, which traps solids, has to be removed after each filtration. The operation of the device is not suitable for sampling from a continuous stream.